MANNING Regina O. Obe Leo S. Hsu FOREWORD BY PAUL RAMSEY IN ACTION www.it-ebooks.info PostGIS in Action www.it-ebooks.info www.it-ebooks.info PostGIS in Action REGINA O. OBE LEO S. HSU MANNING Greenwich (74° w. long.) Download from Wow! eBook <www.wowebook.com> www.it-ebooks.info For online information and ordering of this and other Manning books, please visit www.manning.com. The publisher offers discounts on this book when ordered in quantity. For more information, please contact Special Sales Department Manning Publications Co. 180 Broad Street Suite 1323 Stamford, CT 06901 Email: orders@manning.com ©2011 by Manning Publications Co. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by means electronic, mechanical, photocopying, or otherwise, without prior written permission of the publisher. 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Development editor: Sebastian Sterling 180 Broad Street Copyeditor: Linda Recktenwald Suite 1323 Typesetter: Marija Tudor Stamford, CT 06901 Cover designer: Marija Tudor ISBN: 9781935182269 Printed in the United States of America 12345678910 –MAL–17161514131211 Download from Wow! eBook <www.wowebook.com> www.it-ebooks.info v brief contents PART 1 LEARNING POSTGIS 1 1 ■ What is a spatial database? 3 2 ■ Geometry types 33 3 ■ Organizing spatial data 53 4 ■ Geometry functions 80 5 ■ Relationships between geometries 117 6 ■ Spatial reference system considerations 153 7 ■ Working with real data 173 PART 2 PUTTING POSTGIS TO WORK . 201 8 ■ Techniques to solve spatial problems 203 9 ■ Performance tuning 241 PART 3 USING POSTGIS WITH OTHER TOOLS . 277 10 ■ Enhancing SQL with add-ons 279 11 ■ Using PostGIS in web applications 312 12 ■ Using PostGIS in a desktop environment 345 13 ■ PostGIS raster 371 Download from Wow! eBook <www.wowebook.com> www.it-ebooks.info BRIEF CONTENTS vi Download from Wow! eBook <www.wowebook.com> www.it-ebooks.info vii contents foreword xv preface xvii acknowledgments xix about this book xxi about the cover illustration xxviii PART 1 LEARNING POSTGIS . 1 1 What is a spatial database? 3 1.1 Thinking spatially 3 Introducing the geometry data type 6 1.2 Modeling 7 Imagine the possibilities 8 1.3 Introducing PostgreSQL and PostGIS 9 PostgreSQL strengths 9 ■ PostGIS, adding GIS to PostgreSQL 13 ■ Alternatives to PostgreSQL and PostGIS 14 ■ What works with PostGIS 15 1.4 Getting started with PostGIS 16 Verifying version of PostGIS and PostgreSQL 17 ■ Creating geometries with PostGIS 17 Download from Wow! eBook <www.wowebook.com> www.it-ebooks.info CONTENTS viii 1.5 Working with real data 20 Loading comma-separated data 21 ■ Spatializing flat file data 22 ■ Loading data from spatial data sources 25 1.6 Using spatial queries to analyze data 28 Proximity queries 29 ■ Viewing spatial data with OpenJUMP 30 1.7 Summary 31 2 Geometry types 33 2.1 Geometry columns in PostGIS 34 The geometry_columns table 34 ■ Interacting with the geometry_columns table 37 2.2 A panoply of geometries 38 What’s a geometry? 38 ■ Points 39 ■ Linestrings 40 Polygons 41 ■ Collection geometries 43 ■ Curved geometries 47 ■ 3D geometries 51 2.3 Summary 52 3 Organizing spatial data 53 3.1 Spatial storage approaches 53 Heterogeneous geometry columns 54 ■ Homogeneous geometry columns 56 ■ Table inheritance 57 3.2 Modeling a real city 60 Modeling using a heterogeneous geometry column 61 Modeling using homogeneous geometry columns 64 Modeling using inheritance 66 3.3 Using rules and triggers 69 Rules versus triggers 69 ■ Using rules 71 Using triggers 73 3.4 Summary 78 4 Geometry functions 80 4.1 Constructors 81 Creating geometries from well-known text and well-known binary representations 81 ■ Autocasting in PostgreSQL/PostGIS 83 4.2 Outputs 84 Well-known text and well-known binary 85 ■ Keyhole Markup Language 85 ■ Geography Markup Language 86 Download from Wow! eBook <www.wowebook.com> www.it-ebooks.info CONTENTS ix Geometry JavaScript Object Notation 86 ■ Scalable Vector Graphics 86 ■ Geohash 87 ■ Examples of output functions 87 4.3 Accessor functions: getters and setters 88 Getting and setting spatial reference system 88 ■ Transform to a different spatial reference 89 ■ Geometry type 90 Coordinate and geometry dimensions 91 ■ Geometry validity 92 ■ Number of points that define a geometry 93 4.4 Measurement functions 94 Planar measures for geometry types 95 ■ Geodetic measurement for geometry types 96 ■ Measurement with geography type 98 4.5 Decomposition 99 Boxes and envelopes 99 ■ Coordinates 101 Boundaries 102 ■ Point marker for a geometry: centroid, point on surface, and nth point 103 ■ Breaking down multi and collection geometries 105 4.6 Composition 108 Making points 108 ■ Making polygons 110 ■ Promoting single to multi geometries 112 4.7 Simplification 112 Coordinate rounding using ST_SnapToGrid 113 Simplifying geometries 114 4.8 Summary 115 5 Relationships between geometries 117 5.1 Introducing spatial relationship functions 118 5.2 Intersections 119 Segmenting linestrings with polygons 120 ■ Clipping polygons with polygons 121 5.3 Specific intersection relationships 123 Interior, exterior, and boundary of a geometry 123 ■ Contains and Within 125 ■ Covers and CoveredBy 127 ContainsProperly 128 ■ Overlapping geometries 129 Touching geometries 129 ■ Crossing geometries 130 Disjoint geometries 131 5.4 The remainder: ST_Difference and ST_SymDifference 131 5.5 Nearest neighbor 134 Intersects with tolerance 135 ■ Finding N closest objects 135 Using SQL Window functions to number results 137 Download from Wow! eBook <www.wowebook.com> www.it-ebooks.info [...]... with a Graphing and accessing spatial analysis libraries with PL/ R 292 Getting started with PL/R 292 Saving datasets and plotting 293 Using R packages in PL/R 296 Quick primer on rgdal 298 Getting PostGIS geometries into R spatial objects 301 Outputting plots as binaries 304 ■ ■ ■ ■ ■ 10.5 PL/Python 304 Installing PL/Python 304 Our first PL/Python function 306 Using Python packages 306 Geocoding with... http://www.postgresonline.com and http://www.bostongis.com About the title By combining introductions, overviews, and how-to examples, the In Action books are designed to help learning and remembering According to research in cognitive science, the things people remember are things they discover during self-motivated exploration Although no one at Manning is a cognitive scientist, we are convinced that for learning... 11.3 Using GeoServer 324 Installing GeoServer 324 Setting up PostGIS workspaces 325 Accessing PostGIS Layers via GeoServer WMS/WFS 326 ■ ■ 11.4 Basics of OpenLayers and GeoExt Using OpenLayers 328 GeoExt 333 11.5 ■ 327 Enhancing OpenLayers with Displaying data with server-side web scripting 337 Using PostGIS output functions with PHP 337 Displaying data in Google Earth 340 Loading custom layers with... during its crossing of the salt flats, the navigator can use a ruler to measure from the first intersection point to the second intersection point Let’s go through this with a higher level of abstraction We start with two geometries: a linestring and a polygon We overlay one atop the other and find the intersection of the two geometries A line intersected with a polygonal area yields the linestring... ■ 8.3 Slicing and splicing linestrings 221 Create linestrings from points 221 smaller segments 223 8.4 Slicing and splicing polygons ■ Break linestrings into 227 Create a single multipolygon from many multipolygon records 227 Tessellate areas 228 Create equal-area slices 231 ■ 8.5 ■ Translating, scaling, and rotating geometries 235 Move a geometry along X, Y, Z 236 Increase and decrease size of geometry... summary 357 Adding a PostGIS connection 359 Viewing and filtering PostGIS data 360 Connecting with other spatial databases 361 Loading other vector and raster layers 361 Exporting data 362 Summary 362 ■ ■ ■ ■ 12.4 uDig ■ 362 Feature summary 363 Connecting to PostGIS and other spatial databases 364 Viewing and filtering PostGIS data 365 Exporting data 365 Summary 366 ■ ■ ■ ■ www.it-ebooks.info Download from... for intersections and measuring distances 204 Convert to different units of measurement 207 Measure large distances 209 Choose spatial reference systems when measuring area 212 ■ ■ 8.2 Data tagging 215 Techniques for generating dummy data 215 Tag data to a specific region 216 Snapping points to closest linestring 217 Geocoding an address to a point on a street 219 ■ ■ ■ 8.3 Slicing and splicing linestrings... different approaches for storing data in PostgreSQL /PostGIS You’ll learn how to store multiple kinds of geometries in a single geometry column as well as how to control what kinds of geometries can be stored in a column using constraints and built -in PostGIS management functions We’ll cover www.it-ebooks.info Download from Wow! eBook PostgreSQL table inheritance and how to use it... and then making a cut With spatial support all you need to do is to reformulate the question slightly as “Find all houses within a two-mile radius of the coastline.” A spatially enabled database can intrinsically work with data types like coastlines (modeled as linestrings), buffer zones (modeled as polygons), and houses (modeled as points) As with most things worth pursuing in life, nothing comes without... your eyes and mind to something beyond the mundane world of numbers, dates, and strings Let’s get started 1.1.1 Introducing the geometry data type The entirety of 2D mapping can be accomplished with three basic geometries: points, linestrings, and polygons We can model physical geographical entities with these basic building blocks This process is intuitive and interesting For example, an interstate highway . MANNING Regina O. Obe Leo S. Hsu FOREWORD BY PAUL RAMSEY IN ACTION www.it-ebooks.info PostGIS in Action www.it-ebooks.info www.it-ebooks.info PostGIS in Action REGINA O. OBE LEO S. HSU MANNING Greenwich. street 219 8.3 Slicing and splicing linestrings 221 Create linestrings from points 221 ■ Break linestrings into smaller segments 223 8.4 Slicing and splicing polygons 227 Create a single multipolygon. LEARNING POSTGIS . 1 1 What is a spatial database? 3 1.1 Thinking spatially 3 Introducing the geometry data type 6 1.2 Modeling 7 Imagine the possibilities 8 1.3 Introducing PostgreSQL and PostGIS